Solid propellant management control system and method

ABSTRACT

Systems and methods of controlling solid propellant burn rate, propellant gas pressure, propellant gas pressure pulse shape, and propellant gas flow rate, rely on the position of a throttling valve. A throttling valve that is movable to a control position is disposed downstream of, and in fluid communication with, a solid propellant gas generator, and in parallel with a plurality of reaction control valves. The solid propellant in the solid propellant gas generator is ignited, to thereby generate propellant gas. The throttling valve is moved to a control position to attain a desired solid propellant burn rate, propellant gas pressure, and/or propellant gas pressure pulse shape.

TECHNICAL FIELD

The present invention generally relates to propellant gas generation and, more particularly, to a system and method of managing propellant gas generation by a solid propellant.

BACKGROUND

Solid propellant gas generators are used in rockets, missiles, interceptors, and various other vehicles and environments. For example, solid propellant gas generators may be used to generate propellant gas for both vehicle propulsion and direction control for missiles, munitions, and various spacecraft. A solid propellant gas generator typically includes a vessel that defines a combustion chamber within which one or more solid propellant masses are disposed. The solid propellant masses, when ignited, generate high-energy propellant gas. Depending upon the particular end-use system in which the solid gas generator is installed, the propellant gas may be supplied, or at least selectively supplied, to a rocket motor and/or reaction jets that may vary the thrust, pitch, yaw, roll or spin rate and other dynamic characteristics of a vehicle in flight, and/or to a gas turbine to generate backup power.

As is generally known, once a solid propellant mass is ignited, propellant gas generation continues until the entire mass is consumed. As is also generally known, the burn rate of a solid propellant mass may vary with the pressure in the combustion chamber. For example, if the combustion chamber pressure increases, the solid propellant burn rate increases. Conversely, if the combustion chamber pressure decreases, the propellant burn rate decreases. One way of controlling combustion chamber pressure, and thus propellant burn rate, is by controlling the effective flow area of a supply passage downstream of the combustion chamber. For example, if the effective flow area of the flow passage decreases, combustion chamber pressure increases, and vice-versa.

Various systems and methods have been developed for varying the effective flow area of a solid propellant gas generator supply passage. Such systems and methods include throttling propellant gas flow from the combustion chamber using a fixed or variable area orifice, throttling propellant gas flow from the combustion chamber via a variable position valve, and including multiple propellant grains, which are then selectively ignited. Although these systems and methods are effective, each suffers certain drawbacks. For example, the present systems and methods can significantly affect overall gas generator efficiency, and may rely on fairly complex, relatively heavy, and or relatively costly components and control systems.

Hence, there is a need for a system and method of controlling solid propellant burn rate and flexible vehicle attitude and divert control that does not significantly affect overall efficiency and/or does not rely on fairly complex, relatively heavy, and/or relatively costly components and control systems. The present invention addresses one or more of these needs.

BRIEF SUMMARY

In one embodiment, and by way of example only, a solid propellant management control system includes a vessel, a solid propellant, a plurality of reaction control valves, a throttling valve, and a controller. The vessel defines a combustion chamber. The solid propellant is disposed within the combustion chamber, and is configured to generate propellant gas upon being ignited. The reaction control valves are in fluid communication with the combustion chamber, are each coupled to receive reaction control signals, and are each responsive to the reaction control signals it receives to selectively move between a closed position and a full-open position. The throttling valve is in fluid communication with the combustion chamber and is coupled to receive throttling valve control signals. The throttling valve is responsive to the throttling control signals to move to a control position that results in a desired combustion chamber pressure. The controller is operable to selectively supply the reaction control signals and the throttling valve control signals.

In another exemplary embodiment, a method of managing propellant gas generation includes disposing a solid propellant in a vessel and disposing a plurality of reaction control valves downstream of, and in fluid communication with, the vessel. Each of the reaction control valves is movable between a closed position and a full-open position. A throttling valve is disposed downstream of, and in fluid communication with, the vessel, and is movable to a plurality of control positions. The solid propellant is ignited in the vessel to thereby generate propellant gas, and the throttling valve is moved to a control position to attain a desired propellant gas pressure.

Other independent features and advantages of the preferred solid propellant management control system and method will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and

FIG. 1 is a functional block diagram of an exemplary embodiment of a solid propellant gas management system that may be used to implement a projectile reaction control system;

FIGS. 2 and 3 each depict exemplary alternative configurations of a propellant gas flow ejector that may be used to implement the system of FIG. 1; and

FIG. 4 is a graph that depicts combustion chamber pressure versus time for an exemplary mission profile during which the combustion chamber pressure is controlled by controlling the position of the throttling valve in the system of FIG. 1.

DETAILED DESCRIPTION OF VARIOUS PREFERRED EMBODIMENTS

The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. In this regard, although the systems and methods are described herein as being implemented in a vehicle, the systems and methods may also be used in energy storage and/or generation systems.

Turning first to FIG. 1, a functional block diagram of an exemplary embodiment of a solid propellant gas management system 100 is depicted. The system 100 includes a solid propellant gas generator 102, a plurality of reaction control valves 104 (e.g., 104-1, 104-1, 104-3, . . . 104-N), a throttling valve 106, and a controller 108, which may all be disposed within a projectile body 110. The gas generator 102 includes a vessel 112 that defines a combustion chamber 114 in which a solid propellant 116 is disposed. The manner in which the solid propellant 116 is formed and subsequently loaded into the combustion chamber 114 are generally well known, and will thus not be further discussed. Moreover, the particular type of solid propellant 116 may vary. Some non-limiting examples of solid propellant 116 include ammonium nitrate and ammonium perchlorate. No matter the particular solid propellant 116 that is used, upon being ignited by an igniter 118, the solid propellant 116 produces propellant gas, which is directed toward the reaction control valves 104 and the throttling valve 106 via, for example, a suitable manifold 122. As FIG. 1 also depicts, the system 100 may additionally include, for example, a main thrust nozzle 120 and, if needed or desired, an associated control valve 121.

The reaction control valves 104 are each in fluid communication with the combustion chamber 114 via the manifold 122, and are each in fluid communication with a downstream thrust nozzle 124 (e.g., 124-1, 124-2, 124-3, . . . 124-N). The reaction control valves 104 are each coupled to receive reaction control signals from the controller 108, and are each responsive to the reaction control signals it receives to selectively move between a closed position and a full-open position to thereby prevent and allow, respectively, propellant gas flow to its associated thrust nozzle 124. It will be appreciated that the reaction control valves 104 may be implemented using any one of numerous valve types and configurations now know or developed in the future, and that the number of reaction control valves 104 may vary. Some non-limiting examples of suitable valve types include suitably configured poppet valves, pintle valves, and fluidic diverter valves. It will additionally be appreciated that the thrust nozzles 124, which may also vary in number and configuration, are preferably arranged to provide suitable attitude and divert control for the projectile body 110.

The throttling valve 106 is in fluid communication with the combustion chamber 112 via the manifold, and is in fluid communication with a downstream propellant gas flow ejector 126. The throttling valve is coupled to receive throttling valve control signals from the controller 108, and is responsive to the throttling valve control signals to move to a control position. That is, the throttling valve 106, in response to the throttling valve control signals, may be moved to a closed position, to a full-open position, or to any one of numerous valve positions between the closed and full-open positions. In the closed position, the throttling valve 106 fluidly isolates the propellant gas flow ejector 126 from the combustion chamber 114. Conversely, in any one of the open positions, the throttling valve 104 fluidly couples the combustion chamber 114 to the propellant gas flow ejector 126. Thus, if the solid propellant 116 is ignited and producing propellant gas, the control position of the throttling valve 106 may be used to control propellant gas flow to and through the gas flow ejector 126. Hence, the control position of the throttling valve 106 may concomitantly be used to control the pressure in the combustion chamber 114, and thus the burn rate of the propellant.

Before proceeding further, it is noted that the propellant gas flow ejector 126 is preferably configured such that when propellant gas is discharged from the propellant gas flow ejector 126 the attitude of the projectile body 110 is not affected. It will be appreciated that the propellant gas flow ejector 126 may be variously implemented to achieve this result. For example, as FIG. 2 depicts, the propellant gas flow ejector 126 may be configured to discharge propellant gas axially out of the projectile body 110. With this configuration, the propellant gas that is discharged from the propellant gas flow ejector 126 may supply added forward thrust for the projectile body 110. In another exemplary configuration, which is depicted in FIG. 3, the propellant gas flow ejector 126 is configured with opposing discharge nozzles 302. With this configuration, a zero net thrust (or at least a substantially zero net thrust) is exerted on the projectile body 110 as a result of propellant gas flow through the propellant gas flow ejector 126.

Returning once again to FIG. 1, the controller 108, at least in the depicted embodiment, is configured to supply an initiation signal to the igniter 118 and, as noted above, reaction control signals and throttling valve control signals to the reaction control valves 104 and the throttling valve 106, respectively. The initiation signal supplied to the igniter 118 causes the igniter 118 to ignite the solid propellant 116, which in turn generates the propellant gas. It will be appreciated that in alternative embodiments the initiation signal could be supplied from other, non-illustrated devices or systems. As FIG. 1 also depicts, the controller 108 may also be in operable communication with a flight computer 122. The flight computer 122, which may be variously implemented and configured, is operable to supply flight control signals to the controller 108 that are at least representative of a commanded projectile flight path. The controller 108 is responsive to the flight control signals to selectively supply the reaction control signals and the throttling valve control signals. It will additionally be appreciated that the controller 108 and flight computer 122, and their associated functions, could be integrated into a single device.

The controller 108 may be configured to implement either open loop control or closed loop control of the throttling valve 106. If it implements closed loop control, the system 100 may additionally include one or more sensors 128 (only one depicted in FIG. 1). The sensors 128, if included, preferably sense one or more parameters representative of the pressure in the combustion chamber 114, and supply a feedback signal representative thereof to the controller 108. The number and type of sensors 128 may vary, and may include one or more pressure sensors, temperature sensors, valve position sensors, various combinations of each, or all of these sensors. If one or more pressure sensors are included, these sensors preferably sense propellant gas pressure in or downstream of the combustion chamber 112. If one or more temperature sensors are included, these sensors preferably sense propellant gas temperature in or downstream of the combustion chamber 112. If one or more valve position sensors are included, these sensors preferably sense the control position of the throttling valve 106.

As was previously noted, the position of the throttling valve 106 controls propellant gas flow rate to and through the gas flow ejector 126, and thus combustion chamber pressure, and propellant burn rate. The position of the throttling valve 106 may also be used, if needed or desired, to control the generation and shape of pressure pulses in the combustion chamber 114. As an illustrative example, FIG. 4 graphically depicts an exemplary combustion chamber pressure versus time for a particular mission profile during which the combustion chamber pressure is controlled by controlling the control position of the throttling valve 106. As may be seen from this particular mission profile, upon ignition of the solid propellant 116, at time t₀, the amount of thrust that is needed to propel and navigate the projectile body 110 corresponds to a combustion chamber pressure of P₃. The controller 108, based on the flight control signals supplied thereto from the flight computer 122, moves the throttling valve 106 to a control position that results in this combustion chamber pressure.

Thereafter, at time t₁, the amount of thrust that is needed to propel and navigate the projectile body 110 decreases significantly. Thus, controller 108 moves the throttling valve 106 to a control position that results in the combustion chamber pressure being reduced to a pressure of P₁. That is, the throttling valve 106 is moved to a more open position, relative to its position between times t₀ and t₁, resulting in more flow out the gas flow ejector 126. The throttling valve 106 remains in this position until time t₂, at which time the flight computer 122 informs the controller 108 that more thrust is needed. In response, the controller 108 moves the throttling valve 106 to a more closed position, causing relatively less gas to flow out of the gas flow ejector 126 and combustion chamber pressure to increase to the P₂ pressure.

The combustion chamber pressure is held at the P₂ pressure until time t₃, at which time the flight computer 122 informs controller 108 that even more thrust is needed. In response, the controller moves the throttling valve 106 to an even more closed position. As a result, even less gas flows out the gas flow ejector 126 and combustion chamber pressure increases to the P₄ pressure. In accordance with this mission profile, the P₄ pressure is maintained until time t₄. It will be appreciated that the relative times and pressure magnitudes, and the pressure pulse shapes depicted in FIG. 4 are merely exemplary and may vary to meet a desired mission profile. It will additionally be appreciated that features of the solid propellant 116 and/or the solid propellant itself may be varied to provide a desired pressure profile.

In addition to the above, it is noted that in some instances the controller 108 may command all of the valves 104, 106, and 121 (if included) to open positions, or command various combinations of the valves 104, 106, 121 to open and closed positions, to control propellant burn rate, vehicle thrust, and/or maneuvering. For example, the controller 108 may command all of the reaction control valves 104 closed and the throttling valve 106 and main thrust nozzle control valve 121 (if included) opened, to maximize axial vehicle thrust. In addition, selected opposing reaction control valves 104 can be closed along with the throttling valve 106 and/or main thrust nozzle control valve 121 (if included) to maximize an attitude or divert maneuver. It will be appreciated that these are merely exemplary of numerous valve position combinations that may be implemented, and that the valve position combinations may vary depending, for example, on the types of valves that are used (e.g., fluidic valve, poppet valve, pintle valve, etc.).

The systems and methods disclosed herein provide for the selective or collective control of solid propellant burn rate, combustion chamber pressure and pulse shapes, and propellant gas flow. The systems and methods thus conserve propellant utilization, which can extend burn duration, range, and mission flexibility of projectile systems and backup power systems. The disclosed systems and methods provide increased efficiency and increased thrust control flexibility relative to current systems and methods, and do so with an overall lighter weight system.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims. 

1. A solid propellant management control system, comprising: a vessel defining a combustion chamber; a solid propellant disposed within the combustion chamber, the solid propellant configured to generate propellant gas upon being ignited; a plurality of reaction control valves in fluid communication with the combustion chamber, each reaction control valve coupled to receive reaction control signals and responsive thereto to selectively move between a closed position and a full-open position; a throttling valve in fluid communication with the combustion chamber and coupled to receive throttling valve control signals, the throttling valve responsive to the throttling control signals to move to a control position that results in a desired combustion chamber pressure; and a controller operable to selectively supply the reaction control signals and the throttling valve control signals.
 2. The system of claim 1, further comprising: a plurality of reaction control thrust nozzles, each reaction control thrust nozzle disposed downstream of, and in fluid communication with, one of the reaction control valves, each reaction control thrust nozzle configured to generate a thrust when propellant gas flows there-through; and an axial thrust nozzle disposed downstream of, and in fluid communication with, the throttling valve, the axial thrust nozzle configured to generate an axial thrust when propellant gas flows there-through.
 3. The system of claim 1, further comprising: a plurality of reaction control thrust nozzles, each reaction control thrust nozzle disposed downstream of, and in fluid communication with, one of the reaction control valves, each nozzle configured to generate a thrust when propellant gas flows there-through; and a plurality of null thrust nozzles disposed downstream of, and in fluid communication with, the throttling valve, the null thrust nozzles each configured to generate a thrust in opposing directions when propellant gas flows there-through.
 4. The system of claim 1, further comprising: a main thrust nozzle in fluid communication with the combustion chamber to at least selectively receive propellant gas therefrom.
 5. The system of claim 1, further comprising: a manifold in fluid communication with the combustion chamber, each reaction control valve, and the throttling valve.
 6. The system of claim 1, further comprising: a flight computer operable to supply flight control signals representative of a commanded aircraft flight path, wherein the controller is responsive to the flight control signals to selectively supply the reaction control signals and the throttling valve control signals.
 7. The system of claim 1, wherein the controller is further operable to selectively supply the throttling valve control signals to control solid propellant burn rate.
 8. The system of claim 1, wherein the controller is further operable to selectively supply the throttling valve control signals to control propellant gas pressure in the combustion chamber.
 9. The system of claim 1, wherein the controller is further operable to selectively supply the throttling valve control signals to control generation of propellant gas pressure pulses in the combustion chamber.
 10. The system of claim 1, wherein: the propellant gas pressure pulses each have a pulse shape; and the controller is further operable to selectively supply the throttling valve control signals to control the pulse shape of the propellant gas pressure pulses.
 11. The system of claim 1, wherein the throttling valve is selected from the group consisting of a pintle valve and a poppet valve.
 12. The system of claim 1, further comprising: a sensor operable to sense a parameter representative of combustion chamber pressure and to supply a feedback signal representative thereof to the control, wherein the controller is responsive to the feedback signal to selectively supply the throttling valve control signals.
 13. The system of claim 12, wherein the sensor includes one or more of a propellant gas temperature sensor, a propellant gas pressure sensor, and a throttling valve position sensor.
 14. A method of managing propellant gas generation, comprising the steps of: disposing a solid propellant in a vessel; disposing a plurality of reaction control valves downstream of, and in fluid communication with, the vessel, each of the reaction control valves movable between a closed position and a full-open position; disposing a throttling valve downstream of, and in fluid communication with, the vessel, the throttling valve movable to a plurality of control positions; igniting the solid propellant in the vessel to thereby generate propellant gas; moving the throttling valve to a control position to attain a desired propellant gas pressure.
 15. The method of claim 14, further comprising: controlling the control position of the throttling valve to control solid propellant burn rate.
 16. The method of claim 14, further comprising: controlling the control position of the throttling valve to control generation of propellant gas pressure pulses in the vessel.
 17. The method of claim 16, wherein the propellant gas pressure pulses each have a pulse shape, and wherein the method further comprises: controlling the control position of the throttling valve to control the pulse shape of the propellant gas pressure pulses.
 18. The method of claim 14, further comprising: disposing an reaction control thrust nozzle downstream of each reaction control valve, each reaction control thrust nozzle configured to generate a thrust when propellant gas flows there-through; and at least partially controlling the thrust that may be generated by each nozzle by controlling the control position of the throttling valve.
 19. The method of claim 14, further comprising: controlling the position of the throttling valve based on a vehicle mission profile.
 20. The method of claim 14, further comprising: controlling the control position of the throttling valve to control mass flow rate of the propellant gas from the vessel through the throttling valve; and ejecting the propellant gas that flows through the throttling valve in one or more directions that result in a substantially zero net thrust. 